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vasanvasan 01-13-2006 01:46 PM

No Expansion Tank for Water Heater

I bought this house recently and I have Gas Water Heater and Weil McLein Water Boiler for heating. There is an expansion tank installed on the Hot Water side (where heated water comes out of boiler) of the boiler. And there is no expansion tank installed around the Water Heater. Is this configuration OK? I get this doubt becuase I have read in many posts that Expansion Tank must be installed on the cold water side of the Water Heater.

In my boiler I have Pressure/Temperature gauges in two places.
1. One where the heater water comes out of boiler
2. and another one is installed on the return water pipe taht enters boiler.

1st gauge reads 30 psi and 180 farenheit. 2nd gauge reads 25 psi and 170 farenheit. Why is my return water so hot? Shouldn't it be cold? Is this a problem?

Thanks for your help.
- Vasan

justdon 01-18-2006 10:16 AM

Cant address the hot water heat issue, because I have no experience.

It is NICE to have an expansion tank on the water heater as you mention. Maybe a one way valve before that. otherwise every time your water heater is cycling and getting hot the water expands and pushes itself back in the supply pipe and runs back thru your water meter, then back again. You guessed it, the meter charges you for every time it goes thru.(the right way, and doesnt subtract for the wrong way) IF you live somewhere without a meter it doesnt make much difference. But I am just a shade tree d-i-y handy guy.

oddjob 01-18-2006 10:44 PM

Most water meters I have seen have check valves built into them.

DanBress 12-12-2007 07:43 PM

I also have a water boiler heating system that does not have an expansion tank. It does have a pipe(pressure release?) that drains into my utility sink. I have noticed this dripping from time to time. When I purchased the home I was told I should add an expansion tank. Can anyone tell me how i would go about doing this?

scorrpio 12-13-2007 11:16 PM

In a closed system, a good place to use expansion tank is at the fill valve. A bladder style tank precharged at 12psi and coupled to fill valve, air eliminator andvent (see Fill-Trol) Bladder style is better as others inevitably introduce air into radiators.

A 10-degree drop is OK. Especially when radiators are already heated up. When thermostats are just beginning to call for heat and radiators are cold, a 60-70 degree difference is more likely.

Now, about water heater expansion tank. Gotta say, meter explanation is new to me. Most places, code mandates a backflow preventer (which usually is combined in one unit with pressure regulator). A backflow preventer is also usually required before boiler fill valve (so that boiler water does not return to potable supply) and is recommended before a water heater.
Now, as water heats, it expands. If hot water is used regularly, lackof an expansion tank is no biggie - the effect is maximized when a lot of hot water is used up, followed by a period of nonuse. In a system where pressure is already fairly high 110+psi), this can lead to dangerous pressure buildup. No BF preventer before heater means that you also have your cold system to buffer that pressure - still not the best of solutions.
See for info on tanks, and to size your tank. Installation is fairly simple - you put a T into the supply pipe, adda short nipple, a threaded adapter (female) and then connect the tank.

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